Deflection coil arrangement for cathode ray tubes



R. URTEL July 12, 1955 DEFLECTION COIL ARRANGEMENT FOR CATHODE RAY TUBES2 Sheets-Sheet 1 Filed June 27, 1952 FIG. l0.

FlG. I.

INVENTOR. A? U/PTEL HTTO/P/VEY July 12, 1955 R. URTEL 2,71

DEFLECTION COIL. ARRANGEMENT FOR CATHODE RAY TUBES Filed June 27, 1952 2Sheets-Sheet 2 FIG. 30.

FIG. 40.

IN VEN TOR. A. [/ATEZ.

HTTO/P/VE) nite States Patent 1 iiice DEFLEQTIQN COIL ARRANGEMENT FORCATHODE RAY TUBES Rudolf Urtel, Pforzheim, Germany, assignor toInternational Standard Electric Corporation, New York, N. L, acorporation of Delaware Application June 27, 1952', Serial No. 295,946Claims priority, application Germany June 29, 1951 3 Qlaims. (Cl.317--200) This invention relates to deflection coils and moreparticularly to deflection coil windings suitable for use inreproduction cathode ray tubes for television receivers.

Deflection coil systems of two principal types are generally known foruse in controlling the deflection of cathode ray beams. In one of thesetypes the windings of the coil are such that a relatively weak externalfield is produced on this type. Also it has the disadvantage that atboth ends of the deflection coil system the control field extends on asmall distance from the end of the deflection coil arrangement. Thissmall distance of extension is helpful on the cathode end of the tube inthat it does not produce unwanted eddy currents, which may tend todisturb the function of the beam. On the other hand, it is adisadvantage in that the control does not extend any appreciabledistance beyond the coil in the direction of the reproduction screen.

A second well known form of deflection system is provided wherein thedeflection windings provide closed rings about an annular core. Withthis type of arrangement there is a considerable external field and thedeflection field itself extends a substantial distance from both ends ofthe deflection system. This has the advantage of greater control of thebeam in the direction of the screen but the disadvantage that the eddycurrents are set up in the cathode and through portions of the system.These eddy currents may produce detrimental eflects.

According to this invention there is provided a deflection coil systemwhich has the advantage of producing a substantially extending field inthe direction of electron beam control and a rapidly decaying field inthe direction of the cathode and other electrodes.

Accordingly, it is an object of this invention to provide a deflectioncoil system for cathode ray tubes in which the windings on an annularcore are arranged so that at one end of the core a portion of thewindings produces an extended longitudinal deflection field on the axisof the core and at the other end a rapidly decaying of the deflectionfield is produced by another portion of the windings.

The above-mentioned and other features and objects of this invention andthe manner of attaining them will become more apparent and the inventionitself will be best understood by reference to the following descriptionof an embodiment of the invention taken in conjunction with theaccompanying drawings, in which Figs. 1 and la show a diagrammaticperspective and a diagrammatic longitudinal section illustrating thewell known form of coil winding and the field produced therebyrespectively;

Figs. 2 and 2a illustrate a second known form of deflection coil anddeflecting pattern similar to those of Fig. 1;

Figs. 3 and 3a show diagrammatic perspective and a longitudinal sectionsimilar to Figs. 1 and 2;

Figs. 4 and 4a illustrate an alternative winding arrangement and fieldpattern system similar to that shown in Fig. 3.

2,713,131 Patented July 12, 1955 Two principal shapes of windings areknown for the deflection of the cathode ray beam in television tubes.The first shape of windings is known as the so-called shell-core coil,the coils of which consist of individual coil-packs 1 and 2 with closedwindings, and in which those winding components, not contributing to thedeflection, proceed in a plane perpendicular to the tube axis and partlyembrace the neck of the tube. The iron core in of the winding embracesthe coils as a shell. Such a coil arrangement with its field linepattern is shown in Figs. 1 and la. The advantage of this shape of coilis that it exhibits a weak external field which will produce only smalleddy currents in the neighboring parts, such as the axial focussingcoil, the magnet and/or the shieldings. The field lines cross each otherin the plane through the axis in field direction at the saddle point Sclosely in front of the coil, so that a rapidly decaying field is formedin axial direction. On the end of the coil adjacent the cathode thisquickly decaying field has the advantage of a small coupling uf eddycurrent, on the screen-sided end of the coil, however, the disadvantagethat the extension of the field is small in the useful direction.Another drawback of this kind of coils is the poor optico-electronicalquality.

The second shape of windings is known as the socalled ring-core coil,consisting of an iron yoke body embracing the ray and of windings 3 and4, embracing the cross-section of this yoke. Such a coil arrangementwith its field lines is represented in Figs. 2 and 2a. This shape ofcoil is featured by an axially expanded field in useful direction,because the saddle points fall away. Optically the coil is good, but hasthe disadvantage that the extended field in the axial direction causes,on the cathode end, more extensive eddy currents with the focussingdevice. Also the currents energize a strong outer field in the outerwinding parts, which again causes a greater coupling of eddy currents tothe shielding.

The deflecting coil arrangement according to the invention ischaracterized by such a form of windings that the features of thering-core winding, extended field in useful direction, strong outerfield, are combined with the features of the shell-core winding (quicklydecaying field in axial direction, weak outer field).

Some embodiments of the deflecting coil arrangement according to theinvention are represented in the Figs. 3 to 6 of the drawing.

In each of these examples only one set of deflection windings isillustrated since the showing of both sides of deflection windings wouldrender the illustration confusing. It may be considered that thewindings as illustrated in these figures correspond to other vertical orhorizontal section windings of a television receiver cathode ray tube.it will be clearly understood that the other set of windings would bearranged on the core at 90 spacing to the windings shown here and willserve for the co-ordinate deflection.

As pointed out already, it is desired to generate an extended usefulfield in direction of the screen and to have a quickly decaying field inthe direction of the cathode, in order to keep the eddy currents in thefocussing equipment as small as possible and furthermore, if possible,to keep the external field small also.

An example for achieving this field distribution is represented in Fig.3. Within the iron core 5 a shell-core winding 6 is provided. At one endof the windings the wire thereof is bent back so the cross-connection 7overlies the end as shown. By this arrangement the winding componentswhich do not contribute to the deflection are spaced from the front ofthe core and the saddle point S of the field lines of the winding isremoved outwards on this side of the coil and thereby the field isextended in useful direction. In this way one obtains a coil, whichproduces on the screen side of the winding an extended field in usefuldirection, similar to the ring-core coil, but which has a quicklydecaying field in axial direction on the cathode side of the winding,similar to the actual shellcore coil of Fig. 1. Moreover, the part ofthe winding spaced from the end weakens the outer field, as may be seenfrom the field line pattern, thus weakening the eddy currents in theshielding.

In Figs. 4 and 4a is illustrated another embodiment of the deflectioncoil arrangement similar to that shown in Fig. 2. However, in thisarrangement the other end 8 of the winding is also bent back so that itscross-connector 8 also overlies the end of the core as shown. Thiscrossconnector 8 may be arranged to be near the end of the core so thatit will also have some influence on the extension of the deflectionfield in this direction. However, the spacing between the crossconnectors 7 and 8 may be adjusted to give the desired control to thefield longitudinally of the core and winding. It will be realised thatthe longitudinal extension external of the core will have a similareflect on the deflection to that produced by the ring of windings shownin Fig. 2, but will be modified by the cross connections similar to theknown form of Fig. 1 to a controllable extent. Thus, there can beprovided with this system an adjustable control of the extension of thefield longitudinally of the axis of the deflection system. At the sametime, the external field due to the windings radially of the axis isconsiderably reduced.

While I have described above the principles of my invention inconnection with specific apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationto the scope of my invention as set forth in the objects thereof and inthe accompanying claims.

What is claimed is:

1. In a deflection coil system for cathode ray tubes for producing anextended control field axially of the coil system at one end thereof,and a quickly decaying field axially of said coil system at the otherend thereof, the

combination comprising a closed hollow cylindrical core of magneticmaterial, and a winding on said core for producing deflection fields,said winding having a first portion comprising wires extendinglongitudinally internally of said core, a second portion adjacent oneend of said core and extending substantially circumferentially andexternally thereof for interconnecting said wires, said second portionbeing positioned intermediate the ends of said core. to provide asubstantial extension of said deflection fields axially of said core,and a third portion adjacent a second end of said core and extendingsubstantially circumferentially of the axis and externally to produce arapid decay of said deflection fields axially of said core.

2. In a deflection coil system according to claim 1, the combinationwherein said second portion comprises an interconnecting wire arrangedon the outer surface of said core and spaced from one end thereof, theends of said interconnecting wire extending substantially parallel tothe axis of said, core and being connected to said longitudinal wires.

3. In a deflection coil system according to claim 2, the combinationwherein said third portion comprises a wire extending about the outersurface of said core traversely of the axis and spaced a distance fromthe other end less than the spacing of said second portion from itscorresponding end and having its opposite ends extending substantiallyparallel to said axis and connected to said longitudinal wires.

References Citedin the file of this patent UNITED STATES PATENTS2,229,977 Kenyon Jan. 28, 1941 2,237,651 Bruche Apr. 8, 1941 2,240,606Bobb May 6, 1941 2,333.806 Mauerer Nov. 9, 1943 2,455,171 Haantjes Nov.30, 1948 2,565,331 Torsch Aug. 21, 1951 2,570,425 Bocciarelli Oct. 9,1951

